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Radon mitigation

ARMANDO COBO | Posted in General Questions on

A house I’m designing in Illinois, south of St Louis, needs to have a radon mitigation system. The best practice recommendation for radon mitigation, per EPA, BSC and everyone else, is to install a passive ventilation stack from a basement drain tile loop all the way through the roof. We’ve all seen the details before many times.
My question is, if I install an outside AND inside perimeter footing 4″ socked drain tile dumping water into a sump basin, I could assume that radon will go to the sump basin as well. So could I seal the sump basin lid and drain pipes and install a radon vent out of the sump basin instead and dump it outside the house by the rim joist? Or do I still need to have a separate vent stack?

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  1. GBA Editor
    Martin Holladay | | #1

    Several sump manufacturers sell airtight sump lids, and several such systems are designed to integrate a radon mitigation riser pipe. Here is one such system: Radon Mitigation System with Sealed Sump Cover.

    As far as I know, it's still best practice to extend the radon mitigation pipe above the roofline rather than through the rim joist. If you go through the rim joist, you can extend the pipe vertically on the exterior of the siding, but it looks ugly. Running it vertically indoors is better.

  2. Expert Member
    Peter Engle | | #2

    If you are trying to do passive radon mitigation, running the pipe as high as possible, and running it up through the interior of the house are both important. The passive system works on the stack effect, and the warmer the air in the pipe, the more buoyant it is. The EPA also recommends venting above the roofline so that the radon-rich air from the vent dissipates rather than re-entering the house through windows and/or air intakes.

  3. Expert Member
    ARMANDO COBO | | #3

    Thank you much for the link and advise. This is exactly what I need, plus I'll make sure I add a separate stack vent just to make sure we are covered.

  4. onslow | | #4


    I believe you will need to seal the slab edge to the walls in addition to any sump sealing plans. You can't count on the radon gas to cooperatively march to the sump pit. I am still in the process of sealing my own slab which unfortunately is being done after moving in, which entails a lot of box moving.

    Radon as a gas has about a four day half life and decay produces alpha particle energy which has a very short range. Unfortunately, if you lungs are full of it, that energy is imparted to your cells. The daughter particles produced stay put and also decay producing damage. Un-inhaled radon decays into particles that become part of the household dust, which is why I would recommend sealing the edges and cracks in the slab.

    I am not totally convinced that venting low or high will make much difference if you avoid dumping it out next to your ERV intake or similar. The main goal is to keep free radon levels reduced in the living envelope.

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